Enhanced biological carbon consumption in a high CO2 ocean

Area of Science:

• Marine biology
• Oceanography
• Biogeochemistry

Background:

• Oceans absorb significant atmospheric carbon dioxide (CO2), leading to ocean acidification and reduced carbonate saturation.
• Projected CO2 rise threatens marine life, particularly calcifying organisms, with largely unknown ecosystem-level consequences.

Purpose of the Study:

• To investigate the impact of elevated carbon dioxide (CO2) on plankton community's dissolved inorganic carbon consumption.
• To determine how changing CO2 levels affect nutrient uptake and carbon-to-nitrogen stoichiometry in marine plankton.

Main Methods:

• Utilized mesocosm enclosures to maintain natural plankton communities under varying CO2 partial pressures (350, 700, 1,050 microatm).
• Monitored dissolved inorganic carbon consumption and nutrient uptake within the mesocosms.
• Analyzed the stoichiometry of carbon to nitrogen drawdown and organic carbon loss.

Main Results:

• Dissolved inorganic carbon consumption by plankton communities increased with rising CO2 levels, by up to 39% at higher concentrations.
• Nutrient uptake remained constant across different CO2 treatments.
• The carbon:nitrogen drawdown ratio increased significantly with elevated CO2, exceeding the Redfield ratio and indicating greater organic carbon loss.

Conclusions:

• Plankton communities exhibit enhanced carbon consumption under elevated CO2 conditions.
• Increased CO2 alters marine carbon cycling, with potential implications for ecosystem structure and function.
• Biologically driven feedbacks in the ocean play a crucial role in the global carbon cycle and climate change.